By now we've all seen the video of the Aug. 13 stage collapse at the Indiana State Fair moments before country duo Sugarland was to perform. Opening act Sara Bareilles had concluded her set just a half hour before. The collapse injured dozens; many seriously, killing four in the audience immediately, and truss spot operator Nathan Byrd was later pronounced dead at Wishard Hospital. This is the third outdoor show of the summer in which abrupt, heavy winds destroyed some or all of a stage. Cheap Trick's July 17 performance at the Ottawa Bluesfest was cancelled when the roof fell 20 minutes into their set, narrowly missing members of the band and injuring Upstaging driver Sandy Sanderson. On August 7th in Tulsa, OK, winds blew a15-foot video screen off the back of the stage at the Brady Block Party, forcing Flaming Lips' bassist Michael Ivins to leap out of the way.

Prior to the disaster, state fair officials contacted the National Weather Service (NWS) four times between 5:30 p.m. and 8 p.m. The NWS predicted that a thunderstorm would reach the fairgrounds between 9 and 9:30 p.m., expected to contain heavy rain, lightning, strong winds and 1- to 2-inch hail. AccuWeather issued a warning for 60-mph winds at 8:23 p.m. NWS issued a severe thunderstorm warning for the county at 8:39 p.m.

Six minutes later, at 8:45 p.m., the crowd was told that there was bad weather in the area, and if it worsened, the concert could be postponed and were told to seek shelter in a nearby building, but few left. A few minutes later, State Fair director Cindy Hoye and State Police Captain Brad Weaver decided to evacuate the grandstand, but before they could do so, the now famous gust of wind hit the stage at 8:49 p.m. The 60-mph winds were an unanticipated precursor to the actual thunderstorm, which hit 15 minutes later.

Fifteen miles to the northeast, the Indianapolis Symphony's Beatles pops show was playing at the Conner Prairie Park's outdoor stage for 7,000 outdoor concertgoers. It was an 8 p.m. show and was cancelled at 8:19 p.m. when a mandatory evacuation was ordered – 30 minutes before the State Fair tragedy. What was the difference between those two events?

The Symphony's severe weather policy requires evacuation if a storm with lightning is 10 to 15 miles away. They subscribe to a weather service on portable computers that provides detailed information. If they have a large audience, they calculate the time it takes for the audience to get to their vehicles. Working backwards from the speed of the storm front, they estimate how soon it will arrive in the 15-mile radius, adding the time needed to get people evacuated.

The Indiana State Fairground's severe thunderstorm evacuation procedures only specifically address tents and buildings with no mention of how or when to evacuate the grandstand. It does state that patrons are to be notified by loudspeaker if a severe thunderstorm warning is issued by the NWS – which happened 10 minutes before the rigging fell – but that announcement was never made, and firm evacuation orders weren't given.

Even more than seasonal venues, state fairs are limited engagements, which doesn't allow for cancelled shows to be rescheduled. Those who've worked "rain or shine" events understand that the chances of completing a show once a stage roof has been lowered due to inclement conditions are relatively slim, as operating the roof itself can be dangerous in bad weather. Lowering the roof would have, at a minimum, delayed the show, and its eventual load-out, a further detriment.

Meanwhile, Janet Jackson and Lady Antebellum shows at the grandstand this week have been cancelled. The Maroon 5 and Train concert originally scheduled for this Thursday, Aug. 18, will be played at Indianapolis' Conseco Fieldhouse, with all proceeds benefiting the Indiana State Fair Remembrance Fund for the families of those who died and suffered injuries. Many seasonal venues operate for another month, and it would be prudent to immediately review severe weather evacuation plans.